After days of complaints from music fans, the producers behind the 12-12-12 benefit concert for Hurricane Sandy victims denounced scalpers on Friday for reselling tickets to the event on StubHub and other Web sites for many times their face value.

The producers — James Dolan of Madison Square Garden, John Sykes of Clear Channel and the film producer Harvey Weinstein — urged people to shun the tickets popping up in the secondary market and to give to charity instead.

“It’s despicable,” Mr. Weinstein said. “Don’t buy them.”

On Thursday afternoon tickets for the floor in front of the stage were listed for as much as $48,000 while those in the upper level were going for $525 to $3,000.